The design of integrated circuits can be accomplished using various forms of electronic design automation software that allows the circuit designer to create and digitize the shapes and patterns that form an integrated circuit. Integrated circuits and other semiconductor devices consist of several overlaid layers of material and each layer, i.e. each device level, includes an associated layout that must be generated by the designers in cooperation with all of the other device levels, especially the level and features above and below it. The integrated circuit design must comply with several different design rules including rules associated with the device level being designed and rules associated with the interrelationship between the device level being designed and subjacent and superjacent device levels.
The design rules may be established by the customer or they may be established by the mask foundry which dictates the tolerances that the mask foundry can accept in generating the photomasks. The design rules may also be promulgated by the device fabrication facility, also referred to as a foundry, based on the capabilities of processing operations. There are many design rules and each of the design rules must be complied with, in order for a photomask set to be created such that an integrated circuit can be successfully fabricated using the mask set.
The number of design rules associated with an integrated circuit is increasing and design rules are becoming more complex as a result of narrower process windows and more layout-dependent effects taking place in processing operations in advanced technology. The totality of rules is challenging for circuit designers to comprehend collectively but according to conventional practices, this must be done prior to commencing the design of the layout. According to current practices, the designers first consult the design rule manuals which contain voluminous and complex design rules, then query the foundry or foundries for the meaning of the design rules, and then begin designing the layout. After an initial design layout implementation is carried out, a design rule check is performed and the circuit designers must again repeat the steps of consulting the design rule manual and querying the foundry or foundries regarding the design rules. Several iterations of the design process are typically required.
This produces a time-consuming, expensive and inefficient way of designing the layouts of integrated circuits. It would be desirable to address these limitations and shortcomings especially in view of the popularity and proliferation of integrated circuit devices used in various applications in today's world.